"[Since] July 2012 Deutsche Bank has received requests for information from regulators in connection with setting interbank offered rates for various currencies. Deutsche Bank is co-operating with these investigations," says the spokesperson.

Citing unnamed sources, the paper identified Portigon, which is last unit remaining from the breakup of a previously large West German state commercial bank WestLB, as another lender being investigated by BaFin.

Portigon declined to comment and BaFin had not returned communication from IBTimes UK by the time this article was published.

Currently, more than 40 banks still contribute to setting the Euribor inter-bank lending rate, but some institutions are withdrawing from this task.

Earlier this month German bank BayernLB revealed it had withdrawn from the Euribor panel from the beginning of this year for "strategic reasons" and the Euribor-EBF group running the Euribor setting process warned that more could leave following recent bad publicity.

The probe is believed to be connected value-added-tax (VAT) 'carousel fraud', where goods were imported VAT-free then sold on to domestic buyers at a price that includes VAT.

Deutsche Bank said in a statement to IBTimes UK that Fitschen and Krause "are involved in the investigations, as they signed the VAT statement for 2009. The bank corrected this a long time ago voluntarily. Unlike the Public Prosecutor's Office, Deutsche Bank is of the opinion that this correction took place in due time."

In what is believed to be a landmark criminal case in Europe, the litigation, dubbed the 'Milan Derivatives Inquisition,' found the four banks guilty of "aggravated fraud for mis-selling derivatives to the city of Milan" and fined each institution €1m ($1.3m / £800,000) and ordered a "total seizure of €87m."

In addition, nine bank employees were handed suspended jail sentences of up to eight months